#include<bits/stdc++.h>
#define uint unsigned int
#define ll long long
#define ull unsigned long long
#define mid ((l+r)>>1)
#define File(xxx) freopen(xxx".in","r",stdin),freopen(xxx".out","w",stdout)
using namespace std;
namespace IO{
    char buff[1<<21],*p1=buff,*p2=buff;
    char getch(){
        return p1==p2&&(p2=((p1=buff)+fread(buff,1,1<<21,stdin)),p1==p2)?EOF:*p1++;
    }
    template<typename T>
    void read(T &x){
        char ch=getch();int fl=1;x=0;
        while(ch>'9'||ch<'0'){if(ch=='-')fl=-1;ch=getch();}
        while(ch<='9'&&ch>='0'){x=x*10+ch-48;ch=getch();}
        x*=fl;
    }
    template<typename T,typename ...Args>
    void read(T &x,Args& ...args){
        read(x);read(args...);
    }
    char obuf[1<<21],*p3=obuf;
    void putch(char ch){
        if(p3-obuf<(1<<21))*p3++=ch;
        else fwrite(obuf,p3-obuf,1,stdout),p3=obuf,*p3++=ch;
    }
    void pc(const char *s){
    	while(*s)putch(*s),s++;
    }
    char ch[100];
    template<typename T>
    void write(T x){
        if(!x)return putch('0');
        if(x<0)putch('-'),x*=-1;
        int top=0;
        while(x)ch[++top]=x%10+48,x/=10;
        while(top)putch(ch[top]),top--;
    }
    template<typename T,typename ...Args>
    void write(T x,Args ...args){
        write(x),putch(' '),write(args...);
    }
    void flush(){fwrite(obuf,p3-obuf,1,stdout);p3=obuf;}
}
using namespace IO;
const int N=5e5+5;
int n;
int fa[N],s0[N],s1[N];
int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);}
void merge(int x,int y){
	x=find(x),y=find(y);
	s1[x]++;
	if(x^y){
		fa[x]=y;
		s0[y]+=s0[x];
		s1[y]+=s1[x];
	}
}
signed main(){
	File("pairint"); 
	read(n);
	for(int i=1;i<=2*n;i++)
		fa[i]=i,s0[i]=1;
	for(int i=1;i<=n;i++){
		int x,y;
		read(x,y);
		merge(x,y);
	}
	int ans=0;
	for(int i=1;i<=2*n;i++)if(fa[i]==i)
		ans+=min(s0[i],s1[i]);
	write(ans);
	return flush(),0;
}

